Chemical processing of semiconductor wafers and similar substrates is often carried out in large batches, where 20 or 30 wafers are immersed in liquid or subjected to liquid sprays as a group. While this is highly effective for rinsing and drying of wafers, as well as for many conventional acid treatments, it is of questionable economy where extremely expensive wafers or substrates are being processed. Not only do such large-scale batch treatments of wafers multiply potential loss due to malfunction in the processing steps, but batch handling of wafers often interrupts the normal individualized handling and development of more expensive and exotic wafers or substrates.
The present invention was developed to minimize such economic losses by handling only a single wafer. It also adapts readily to existing single wafer production techniques common in the semiconductor industry. Furthermore, in contrast with the treatment of large batches of parallel wafers arranged in a stack, the single wafer process as described herein permits treatment of one wafer surface (by application of liquid sprays) as well as both wafer surfaces (by immersion treatment). It also readily accommodates robotic transfer of each wafer between processing units and other automated handling equipment. Indexing and rotation of each wafer can be controlled to meet precise processing requirements. The use of individual bowls in which process steps for single wafers are conducted minimize the amount of liquid required for wafer processing. The smaller volume requirements permit use of fresh liquid to minimize the contamination that might otherwise be encountered when recirculating liquid in larger volume systems.